Numerous processes for continuously electroplating metal strips have been developed, and a variety of such processes are used commercially. Traditional continuous electroplating processes involve fully submersing a metal strip in an electrolyte solution and applying current to deposit metal ions from the electrolyte solution onto the metal strip, thus forming a coated surface. In the traditional processes, the metal strip traverses the electrolyte solution in a generally horizontal direction, generally vertical direction, or at an angle between these two directions. In most commercial electroplating processes, a plurality of electroplating units (cells) are arranged in series so that the metal strip traverses the electrolyte in a first cell, where it is electroplated, and from there enters into a second cell, where additional coating is added, and so on.
An approach which is different from the traditional electroplating processes is disclosed in U.S. Pat. No. 4,469,565, issued to Hampel, on Sep. 4, 1984 (Hampel). The Hampel patent discloses electroplating of a continuous metal strip using the surface as a cathode and a non-horizontal plate as an anode. The electrolyte is continuously supplied into a space between the metal strip and the anode plate so as to fill completely the space with the electrolyte. The electrolyte in the space between the metal strip and the anode plate continuously flows downward from the force of gravity and is continuously replenished by additional electrolyte supplied into the space.
In most continuous electroplating processes, after the coated metal strip exits the electrolyte solution, it contacts a conductor roll. Typically the metal strip is wrapped around at least a portion of the conductor roll so that the metal strip contacts the conductor roll with some force.
As a result of this contact with the conductor roll, defects can be produced in the metal strip due to imperfections in the conductor roll surface. Some of the imperfections in the conductor roll surface are attributable to the electrolyte solution, which is generally acidic. For example, metal ions in the electrolyte solution can plate onto the conductor roll surface and the electrolyte solution can etch the conductor roll surface. The electrolyte solution can produce anomalies in the surface of the conductor roll. By diluting the electrolyte solution with large quantities of water, the method of the present invention reduces defects in the metal strip that result from the action of the electrolyte solution on the conductor roll.
Unexpectedly, the method of the present invention also reduces and/or eliminates conductor roll surface anomalies that are created in the material of the conductor roll itself and do not appear to be connected to the electrolyte solution. For example, surface finish defects that result from arcing, wherein the metal of the conductor roll is melted and displaced; grooves that are worn into the conductor roll surface; and defects that are called "dot dents," which are random areas of raised metal consisting of the metal of the conductor roll, are significantly reduced and/or eliminated when a large quantity of water rinses the electroplated metal strip before it contacts the conductor roll.